Age-enhancing cognitive ability shows similar attenuation in task evoked brain networks with aging and preclinical AD

Brain aging - with and without pre-clinical Alzheimer's disease (AD) pathology - are associated with deterioration in the brain networks' coherence and/or co-activation/deactivation as well as with decline in most cognitive abilities, paving the road for a network-based conceptualization of the brain normal versus pathological aging. However, certain cognitive abilities, like crystallized memory, improve with age, which complicates the explanation of these changes solely through age-related decline in the brain networks. Using a cross-sectional cohort of 259 participants (62 young, and 197 older), which underwent two task-based (one declining and another improving with age), and one resting-state fMRI scans, plus a positron emission tomography scan (to determine preclinical amyloid accumulation), we found that the brain networks' co-activation/deactivation, but not coherence, significantly attenuate with age and/or AD pathology even in the task for which performance improves by age. Interestingly, we also found that an increase in the networks' co-activation/deactivation, but not coherence, was associated with an improvement in task performance. Finally, we provided preliminary evidence that the brain networks lose their task-evoked deactivations with age before their coherence. These findings shed light on the process of functional aging in the brain networks, differentiate functional aging of the brain networks' coherence at rest versus their task-evoked co-activation/deactivation, and emphasize the more dominant role of the task-evoked brain activity in understanding aging brain function and distinguishing it from preclinical AD.